Need for Speed: ProStreet is a racing game where the player must tune and drive cars on various race tracks. Although it is not a sim racing game, cars handle in a more realistic way than in previous Need for Speed games. The player assumes the role of Ryan Cooper, a former street racer who enters a series of showdown events run by several racing organizations. Each event comprises a number of races where the player must compete against computer-controlled opponents to earn points and cash. Points allow the player to unlock more challenging events and progress through the game, while cash can be used to purchase or upgrade cars. The overall objective of the game is to ultimately confront a number of elite drivers called Kings. By individually beating every King, Cooper will be crowned the Street King.
The game features four race modes: Grip, Drag, Drift, and Speed. Grip races involve the player racing around a circuit over several laps, where the win condition depends on four variations. These include crossing the finish line in the first position or ahead of a class of drivers based on their car performance, recording the best lap time, and recording the best sector times, with each sector representing a section of the circuit. In Drag, the player must be the first to cross a finish line on a short and straight course, changing gears manually. Some also require the player to perform long wheelies. Drag races always start out with a mini-game where the player can gain a good starting grip by heating up car tires while in braked position. Drift races require the player to score points by drifting around bends, while Speed races involve the player maintaining very high speeds on a relatively straight point-to-point course. The win condition of Speed races depends on two variants, which include crossing the finish line in the first position or reaching the highest speed at designated checkpoints. Most races take place in real-world locations such as Texas World Speedway, Portland International Raceway, Mondello Park, and Autopolis.
ProStreet features a large number of cars, ranging from affordable tuner-friendly sedans to exotic cars. Each car can be highly customized, including its performance, handling, and appearance. Body modifications such as spoilers and hoods affect the car's aerodynamics and can be sculpted accordingly. Cars and aftermarket parts are grouped into four tiers that represent performance levels, which are gradually unlocked as the player progresses through the game. Each car can have a maximum of three blueprints associated with it, with each blueprint representing a different customization. Choosing and tuning the right car for the right race mode is critical to complete the game. For example, Grip races favour cars with fast acceleration and strong drag force, while Speed races favour cars with high top speeds and stability. Cars can be damaged or completely totalled in accidents, and the player must often repair them with cash or by using repair markers, which can be awarded in events or bought separately.
In addition to the game's main career mode, ProStreet features a number of predefined and stand-alone events where the player can race against computer-controlled opponents on any track without the consequences of having to spend cash to repair cars. They also serve as social areas for multiple players to compete online or via split screen. Each event has its own leaderboard, allowing the player to compare their records against top players. Although a variety of pre-tuned cars are available for each event, players also have the option to race with their custom cars from the game's career mode. Players may also create their own custom events. Options such as the location, type, and the number of races, as well as the difficulty of computer-controlled opponents and the number of repair markers available, can be individually configured. Both custom events and car blueprints can be shared with other players. Once a blueprint is shared with another player, it can no longer be modified because the records associated with it are tracked on leaderboards. Private leaderboards are automatically created for each custom event that is shared.